The plasma transferred wire arc (“PTWA”) process is a particularly useful high-pressure plasma coating process capable of producing high-quality metallic coatings for a variety of applications, such as the coating of engine cylinder bores. In the PTWA process, a high-pressure plasma is generated in a small region of space at the exit of a plasma torch. A continuously-fed metallic wire impinges upon this region, wherein the wire is melted and atomized by the plasma. High-speed gas emerging from the plasma torch directs the molten metal toward the surface to be coated.
When feeding the wire during the PTWA process, a cylindrical wire guide on the torch head directs the wire by feeding the wire through the wire guide immediately prior to the wire being fed into the plasma jet. The positioning of the wire relative to the plasma jet is critical to the thermal spray process. Thus, the wire guide has an extremely tight tolerance relative to the outer diameter of the wire so as to strictly control the positioning of the wire relative to the plasma jet. However, even with the tight tolerance established between the wire guide and the wire, the wire guide and the wire establish a coaxial relationship which still allows the wire to float to a certain degree since there must be a sufficient amount of space between the wire and the wire guide to allow the wire to pass through the wire guide. This floating of the wire may allow the wire to move from its optimal position when entering the thermal jet of the PTWA process. Since the positioning of the wire in the thermal jet spray is critical to the quality of the PTWA process, such floating can affect the quality of the PTWA process.